Lamp and housing assembly

ABSTRACT

A heat-confining member is provided adjacent to a lead-seal portion of a lamp, and is positioned and proportioned so as to cause a sufficiently uniform temperature gradient at the seal to prevent the seal from cracking. The arrangement is particularly useful with arc tube lamps which operate at high temperatures.

[451 Jan. 18, 1972 United States Patent Miller 3,426,234 2/1969 Hayasakaetal................. 3,494,693 2/1970 Elmel'..............

Pn'maryExaminer-James J. Gill Attomey-Norman C. Fulmer, Henry P. Truesdell, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forrnan [22] Filed: Nov. 14, 1969 iform temperature gradient at the seal am mm an .we "t o a a P. l .B am tt mm m n mm W m mm MW TN-D. IO d ah dm ck T e hh CM Tw n .S M mo m n. r m mm .w uh m rm. IE S b i. mu mdm Em [C m yfr nw .mmw m h w w mawuml. o mmmma mn w flbew w nhnm wm 5 oaome rlApctl-p HMZA H 1 30 Wm 2 51 m WC WA m ml .1 mm M .I 2. C m 8 u 0 n n "m R 6 m 7 m 8 mr M "mam L o M m P Sm A UIF 1]] 1 l 218 6 2 555 5 .l

All?! Qatar! D UNITED STATES PATENTS 3,379,863 Tzrillpnm..................... ..2)[T.3 X

LAMP AND HOUSING ASSEMBLY BACKGROUND OF THE INVENTION Certain lamps have a tendency'to develop cracks in their glass or quartz envelopes at the vicinity of the stem seals where the electrical leads enter the envelopesJSuchcracks are likely to permit air:to enter into, and'anyfill gas to leak out of, the envelopethus destroying the usefulness of' the lamp. This problem of seal failureshas been particularlyprevalent-with arc tube lamps which operate athightemperatures. Such atype of lamp, and a1 reflector housing arrangementltherefore, is disclosed in U.S. Pat. No. 3,379,868 of JohnK. Taillon, issued Apr. .23, 1968 and assigned-to-the same 'assignee as the present invention. y

The aforesaid problem of seal crackinghasheretofore'been partlybut not completely solved by arrangementsfor reducing the operating temperature at the seal region. One technique for reducingthe seal temperature is to increase-the length of the neck portion of the lamp. For example, the aforementioned patent shows an elongated arc tube lamp having a seal at each end thereof andintended for direct current operation whereinthe anode .operates at a higher temperature than the cathode. To reduce the temperature-at the anode seal, the anode neck portionis made relativelylongerzthan the cathode neck portion so that the anode seal will be farther away from the hot operating end of the anode electrode. Another technique shown in the aforementioned patent for reducing the seal temperature, is to cement the seal (particularl-ythe anode seal in the case of alamp intended for direct current operation) to a housing with a cement materialthat. is sufficiently heat conductive so as to conduct some of the heat away from the seal.

In spite of therforegoing measures, cracking of lead 8881551185 remained a problem.

SUMMARY OF THE INVENTION Objects of theinvention-are toprovide-an improved lamp and housing assembly, .and to provide .an arrangement for reducing the likelihoodof cracks occurringtat. lead seals of lamps.

The invention comprises, briefly and in a preferred embodiment, an arrangement of a lamp havingalead-seal, and aheatconfining member positioned adjacentto the lead-seal, the heat-confining member being positioned and proportioned to distribute the temperature at the lead-sealsoas to cause more uniform temperature in the lead-seal region. This more uniform temperature, or reduction in temperature gradient, reduces the likelihood of cracking at tire-sealfThus, contrary to prior art techniques of simply coolin'g'the seal to'reducethe likelihood of cracking,.the invention provides distribution of heat over the seal region to reduce the likelihood of cracking The invention can advantageously be used in combination with means for cooling thelead-seal region.

BRIEF DESCRIPTION OF'TI-IE'DRAWING FIG. 1 is a front view of aprojection lamp and reflectorhousing assembly inaccordance with a preferred-embodiment of the invention,

FIG. 2 is a cross-sectional-side view taken on the line 2-2 of FIG. 1,

FIG. 3 is a cross-sectionalend view of'the assembly taken on the line 33 of FIG. 2', and

FIG. 4 is a perspective view of a preferred embodiment ofa heat-confining member in accordancewith the preferredembodiment of theinvention.

DESCRIPTION OF TI'IEPREFERRED EMBODIMENT The assembly shown in the drawing, is generally similar to that disclosed in the aforesaid U.S. Pat. No. 3,379,868. A compact high-intensity arc tube lamp llwcomprises aquartz envelope having a bulb portion 12.and having. neck portions 13 and 14 extending therefrom on: opposite sideszthereof, on a common axis. Elongated tungsten anode and cathode electrodes 16 and 17 are positioned onfthe axis of the lamp with .theinner-ends thereof spaced apart' within the bulb portion 12, and respectively extending into the anode neck portion 13 and cathode neck portion 14. The outer ends of the anode and .cathode electrodes 16 and 17 are respectively welded to molybdenum foils 1'8 and 19, these-foils in turn being welded to inleads 21 and 22. In the process of'manufacture, the foils 18vand 19. are wettedby the quartz of the necks I3, 14 to provide hermetic seals. The lamp contains an ionizable filling which includes an inert gas such argon and a halogen or metal halide suchas indium iodide ."Eurther details of the lamp 11 and its manufacture are disclosed in U.S. Pat. No. 3,305,289 to Elmer G. Fridrich, issued'Feb. 21, 1967 and assignedtothe same. assignee as the present invention. The lamp shown is intended for direct current operation, which causes the .anode electrode 16 to operate at a considerably higher temperature than the cathode electrode 1.7, and therefore the anode electrode 16 is made thicker and longer than the cathode electrode". I

A reflector'housing 26is provided, preferably made of glass and having an ellipsoidal inner surface covered with a reflective coating 27. A pair of apertures 31, 32 are provided in the wall ofzthehousing26 on a line passing through the near focus 11 of the reflector and transverse to its optical axis. The housing 26 is. shaped to provide inwardly extending collars 33 and 34'at the. apertures 31 and 32, as shown.

Thearc tube 11 ismounted'generally along aline extending 'throughthe apertures 31 .and 32, with the arc region thereof coinciding with the near focus point fl of the reflector. The lead-seal regions and/or the inleads-21, 22 of the lamp extend into therecesses 31 and 32 and are set in a glassy cement 36, for-holding the lamp in correct position, as will be described. Anodeand cathode electrical connection wires 37 and 38 are respectively connected to the anode and cathode inleads 21 and 22, as shown. Further details of the reflector housing 26 are disclosed in the.aforesaid.U.S. Pat. No. 3,379,868.

In accordance with the invention, a heat-confining member 41, preferably in the form of a hollow cylindrical split sleeve made of metal, is fittedin the anode aperture 31 so as to at leastpartially surroundthe anode neck 13 in the region of the stemseal at the foil 18. As best shown in FIG. 4, the heat-confining member 41 preferably comprises a. split sleeve in the form of .a hollow metal cylinder having a slit 42 lengthwise thereof, and provided with one or more tabs 43 extending laterally therefrom at an end thereof. Prior to cementing the anode stem of'lamp 11 inplace, the member 41 is inserted through the anode aperture 31 from the outside of the housing .26, so that the tabs 43-seat againstthe outer rim of the aperture 31 thereby correctly positioning the member 41 in place. The split sleeve member'4lpreferably is normally sprung to a slightly greaterdiameter thanthat, of the aperture 31, so as to seat snugly therein. The inner end of the member 41 preferably is beveled, as shown at 44, in a manner such that the longest dimension-of the member 41 is on the side thereof .away from the slit 42. 'I-hemembe'r-41 is positioned in the aperture 31 so that the slit 42 is'toward the rear of the reflector. This shape and positioning of the heat-confining member 41 provides the greatest heat-confining effect, as will be hereafter described, for the least amount of material in the member 41. After the lamp 11 and heat-confining member 41 are in place, the cement 36 is applied. Ceramic end caps 46 and 47. are then positioned over the anode and cathode apertures '4-1 and 42 on the outside thereof.

As.mentionedabove,.high-temperature arc lamps have been particularly prone to developing cracks at the lead-seals thereof. In the case of'a direct current type of arc tube lamp, asv shown in the drawing, the anode lead-seal, which generally operates ata'higher temperature than the cathode lead-seal, is particularly proneito cracking. The region in which the undesirable crackingoccurs, usually-is in the quartz envelope at the vicinity of the foil .18; however, the region in which cracking mayoccur extends partly down the anode stem 13 toward the bulb portion 12 of the lamp 11. The foregoing are referred to herein as the lead-seal region or portion of the lamp.

It has been found that the invention greatly reduces the likelihood of cracking at the lead-seal region, and the invention can be used in addition to, or in lieu of, the above-mentioned techniques of cooling the lead-seal by making the stem 13 extra long, and by encasing at least part of the lead-seal region with a heat-conductive cement 36. The invention functions by confining heat in the region of the lead-seal, and this is accomplished partly by heat reflection from the inner surface of the member 41, and partially by physical confinement of some of the heat in the region of the lead-seal. This confinement, or partial confinement, of heat in the lead-seal region, provides a more uniform temperature in this region, and thus reduces the likelihood of cracking. Expressed in another way, the theory of the invention is that the undesirable cracking at the lead-seal region was due primarily to irregular temperature gradient in this region, whereby the prior techniques of cooling the lead-seal region have not been entirely effective in reducing the tendency for the cracks to occur, because such cooling techniques had little effect on the temperature gradient; or, in some cases, tended to increase the temperature gradient along the lead-seal region, thereby tending to nullify any beneficial effect from the cooling.

Since the rear inside portion of the reflector 26 has some heat-confining effect, the slit 42 in the member 41 may be quite wide, and the inner end of the member 41 may be cut away in the form of a bevel 44 as shown to shorten the length thereof along the slit 42, without adversely affecting the functioning of the invention. Various types of lamps may benefit from utilizing the invention at one or more lead-seals thereof.

While a preferred embodiment of the invention has been shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art, and will fall within the scope of invention as defined in the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with a lamp having an envelope including an elongated lead-seal extending externally of a bulb portion of the envelope, the improvement comprising a heat-confining member positioned at least partially around and spaced from said lead-seal thereby defining a heat-confining airspace along said lead-seal, said heat-confining airspace being substantially devoid of any matter except air and thereby being adapted to increase the unifonnity of temperature gradient along said lead-seal when said lamp is operating.

2. A combination as claimed in claim 1, in which said heatconflning member is of hollow cylindrical configuration and is positioned around said lead-seal.

3. In a lamp and mounting arrangement wherein said mounting comprises a member having an opening therein and said lamp comprises an envelope including an elongated leadseal extending externally of a bulb portion of the envelope and positioned axially with respect to said opening, the improvement comprising a heat-confining member of substantially hollow cylindrical shape positioned in said opening and extending therefrom so as to be spaced from and at least partly surround said elongated lead-seal of the lamp thereby defining a heat-confining airspace along said lead-seal, said heat-confining airspace being substantially devoid of any matter except air and thereby being adapted to increase the unifonnity of temperature gradient along said lead-seal when said lamp is operating.

4. An arrangement as claimed in claim 3, in which a portion of said mounting member extends substantially parallel to and spaced from said elongated lead-seal, and in which said heatconfining member comprises a resilient split sleeve fitted resiliently in said opening, said split sleeve being oriented so that the split thereof faces toward and is adjacent to said portion of the mounting member whereby said portion of the mounting member aids in confining heat at said smit.

5. An arrangement as claimed |n claim 4, in w ch said split sleeve is provided with one or more tabs extending laterally outwardly at an end thereof and seated against said mounting member adjacent to said opening thereby positioning said split sleeve axially in said opening.

6. An arrangement as claimed in claim 3, in which a portion of said mounting member extends substantially parallel to and spaced from said elongated lead-seal and in which said heatconfining member is beveled at the end thereof extending from said opening, said heat-confining member and the bevel thereof being oriented so that the shorter length of said heatconfining member faces toward and is adjacent to said extending portion of the mounting member whereby said portion of the mounting member aids in confining heat at said beveled end of the heat-confining member.

7. An arrangement as claimed in claim 6, in which said heatconfining member comprises a resilient split sleeve having a split in the wall thereof along the shorter length thereof whereby said portion of the mounting member aids in confining heat at said split.

8. An arrangement as claimed in claim 6, in which said heatconfining member is provided with one or more tabs extending laterally outwardly at the end thereof opposite from said beveled end and seated against said mounting member adjacent to said opening thereby positioning said heat-confining member axially in said opening.

9. An arrangement as claimed in claim 8, including cement interposed in the space between said lead-seal region and the inside of said heat-confining member at the region of said opening in the housing member.

10. In a lamp and reflector arrangement comprising a concave reflector provided with a pair of opposed lateral anode and cathode openings in the wall thereof on a line normal to the optical axis and passing substantially through its focus, and an elongated lamp comprising a bulb portion and anode and cathode stems extending from said bulb portion on opposite sides thereof and terminating in anode and cathode lead-seals, respectively, said lamp being positioned in said reflector along said line and attached to said reflector at said openings, said anode stem comprising a lead-seal region located at least partly within said reflector and outside of the confines of the reflector anode opening, the improvement comprising a hollow cylindrical heat-confining member mounted in said anode opening and extending within said reflector and spaced from and substantially surrounding said anode lead-seal region thereby defining a heat-confining space along said lead-seal region adapted to increase the unifonnity of temperature gradient along said lead-seal region when said lamp is operating.

11. An arrangement as claimed in claim 10, in which said heat-confining member comprises a split sleeve oriented with the split thereof toward the back of the reflector whereby said reflector aids in confining heat at said split.

12. An arrangement as claimed in claim 10, in which the end of said heat-confining member within said reflector is beveled, said beveled heat-confining member being oriented so that the short side thereof is toward the back of the reflector whereby said reflector aids in confining heat at said beveled end of the heat-confining member. 

1. In combination with a lamp having an envelope including an elongated lead-seal extending externally of a bulb portion of the envelope, the improvement comprising a heat-confining member positioned at least partially around and spaced from said leadseal thereby defining a heat-confining airspace along said leadseal, said heat-confining airspace being substantially devoid of any matter except air and thereby being adapted to increase the uniformity of temperature gradient along said lead-seal when said lamp is operating.
 2. A combination as claimed in claim 1, in which said heat-confining member is of hollow cylindrical configuration and is positioned around said lead-seal.
 3. In a lamp and mounting arrangement wherein said mounting comprises a member having an opening therein and said lamp comprises an envelope including an elonGated lead-seal extending externally of a bulb portion of the envelope and positioned axially with respect to said opening, the improvement comprising a heat-confining member of substantially hollow cylindrical shape positioned in said opening and extending therefrom so as to be spaced from and at least partly surround said elongated lead-seal of the lamp thereby defining a heat-confining airspace along said lead-seal, said heat-confining airspace being substantially devoid of any matter except air and thereby being adapted to increase the uniformity of temperature gradient along said lead-seal when said lamp is operating.
 4. An arrangement as claimed in claim 3, in which a portion of said mounting member extends substantially parallel to and spaced from said elongated lead-seal, and in which said heat-confining member comprises a resilient split sleeve fitted resiliently in said opening, said split sleeve being oriented so that the split thereof faces toward and is adjacent to said portion of the mounting member whereby said portion of the mounting member aids in confining heat at said split.
 5. An arrangement as claimed in claim 4, in which said split sleeve is provided with one or more tabs extending laterally outwardly at an end thereof and seated against said mounting member adjacent to said opening thereby positioning said split sleeve axially in said opening.
 6. An arrangement as claimed in claim 3, in which a portion of said mounting member extends substantially parallel to and spaced from said elongated lead-seal and in which said heat-confining member is beveled at the end thereof extending from said opening, said heat-confining member and the bevel thereof being oriented so that the shorter length of said heat-confining member faces toward and is adjacent to said extending portion of the mounting member whereby said portion of the mounting member aids in confining heat at said beveled end of the heat-confining member.
 7. An arrangement as claimed in claim 6, in which said heat-confining member comprises a resilient split sleeve having a split in the wall thereof along the shorter length thereof whereby said portion of the mounting member aids in confining heat at said split.
 8. An arrangement as claimed in claim 6, in which said heat-confining member is provided with one or more tabs extending laterally outwardly at the end thereof opposite from said beveled end and seated against said mounting member adjacent to said opening thereby positioning said heat-confining member axially in said opening.
 9. An arrangement as claimed in claim 8, including cement interposed in the space between said lead-seal region and the inside of said heat-confining member at the region of said opening in the housing member.
 10. In a lamp and reflector arrangement comprising a concave reflector provided with a pair of opposed lateral anode and cathode openings in the wall thereof on a line normal to the optical axis and passing substantially through its focus, and an elongated lamp comprising a bulb portion and anode and cathode stems extending from said bulb portion on opposite sides thereof and terminating in anode and cathode lead-seals, respectively, said lamp being positioned in said reflector along said line and attached to said reflector at said openings, said anode stem comprising a lead-seal region located at least partly within said reflector and outside of the confines of the reflector anode opening, the improvement comprising a hollow cylindrical heat-confining member mounted in said anode opening and extending within said reflector and spaced from and substantially surrounding said anode lead-seal region thereby defining a heat-confining space along said lead-seal region adapted to increase the uniformity of temperature gradient along said lead-seal region when said lamp is operating.
 11. An arrangement as claimed in claim 10, in which said heat-confining member comprises a split sleeve oriented with the split thereof toward the back of the reflector whereby said reflector aids in confining heat at said split.
 12. An arrangement as claimed in claim 10, in which the end of said heat-confining member within said reflector is beveled, said beveled heat-confining member being oriented so that the short side thereof is toward the back of the reflector whereby said reflector aids in confining heat at said beveled end of the heat-confining member. 